Question

Which of the following are chemical changes ?
(i) decaying of wood
(ii) burning of wood
(iii) sawing of wood
(iv) hammering of nail into wood

(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)

Answer 1

(a) (i) and (ii)

The processes in statements (i) and (ii) are chemical changes because decaying and burning causes formation of new compounds; thus they are chemical reactions. The processes in statements (iii) and (iv) are physical changes where no new compounds are formed.